Open Access
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R662
Vol 9 No 6
Research
Circulating immune parameters predicting the progression from
hospital-acquired pneumonia to septic shock in surgical patients
Vera von Dossow1, Koschka Rotard2, Uwe Redlich3, Ortrud Vargas Hein4 and Claudia D Spies5
1Resident in Anesthesiology, Department of Anesthesiology and Intensive Care, Charité – Universitaetsmedizin Berlin, Campus Mitte, Germany
2Resident in Radiology, Clinic for Radiology and Nuclear Medicine, Charité – Universitaetsmedizin Berlin, Campus Benjamin Franklin, Germany
3Resident in Anesthesiology, Department of Anesthesiology, DRK Kliniken Koepenick, Berlin, Germany
4Consultant in Anesthesiology, Department of Anesthesiology and Intensive Care, Charité – Universitaetsmedizin Berlin, Campus Mitte, Germany
5Professor of Anesthesiology, Head of the Department of Anesthesiology and Intensive Care, Charité – Universitaetsmedizin Berlin, Campus Mitte,
Germany
Corresponding author: Claudia D Spies, clauida.spies@charite.de
Received: 3 May 2005 Revisions requested: 27 May 2005 Revisions received: 21 Aug 2005 Accepted: 15 Sep 2005 Published: 12 Oct 2005
Critical Care 2005, 9:R662-R669 (DOI 10.1186/cc3826)
This article is online at: http://ccforum.com/content/9/6/R662
© 2005 von Dossow et al.; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/
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Abstract
Introduction Hospital-acquired pneumonia after surgery is one
of the major causes of septic shock. The excessive inflammatory
response appears to be responsible for the increased
susceptibility to infections and subsequent sepsis. The primary
aim of this study was to investigate immune parameters at the
onset of pneumonia, before the development of subsequent
septic shock. The secondary aim was to investigate the
usefulness of these immune parameters in predicting
progression from hospital-acquired pneumonia to septic shock.
Methods This propective clinical study included 76 patients
with the diagnosis of hospital-acquired pneumonia. Approval
was obtained from the local institutional ethics committee and
relatives of the patients gave informed consent. Of the 76
patients, 29 subsequently developed septic shock. All patients
were included within 4 h of establishing the diagnosis of
hospital-acquired pneumonia (first collection of blood samples
and the analysis of immune mediators). In addition, we defined
early (within 12 h of onset of septic shock) and late (within 72 to
96 h of onset) stages of septic shock for the collection of blood
samples and the analysis of immune mediators. The immune
parameters tumor necrosis factor-α, IL-1β, IL-6, IL-8 and IL-10
as well as the endothelial leucocyte adhesion molecule were
analyzed.
Results In the pneumonia group with subsequent septic shock,
levels of IL-1β, IL-6, IL-8 and IL-10 were significantly increased
before the onset of septic shock compared to patients without
subsequent septic shock. This progression was best predicted
by IL-1β, IL-6, IL-8 and IL-10 (area under the curve ≥ 0.8).
Conclusion At the onset of hospital-acquired pneumonia, a
significant relevant systemic cytokine mediated response had
already been initiated. It might, therefore, be possible to identify
patients at risk for septic shock with these predictive markers
during early pneumonia. In addition, immune modulating therapy
might be considered as adjuvant therapy.
Introduction
Hospital-acquired pneumonia (HAP) is the most common
nosocomial infection and its prevalence within the intensive
care unit (ICU) setting ranges from 31% to 47% [1-4]. The
mortality rate for HAP remains high at 20% to 50% [5-7]. HAP
in surgical patients is especially characterized by the high fre-
quency of early onset infections and the high proportion of
Gram-negative bacteria and staphylococci isolated [8]. Mor-
tality rates are between 19% and 45% for patients who con-
tract postoperative pneumonia after major surgery [9]. A
review by Friedman et al. [10] shows that incidents of HAP as
a cause of septic shock have increased in the past decades
and this has been accompanied by only a limited improvement
in survival. In addition, the study of Martin et al. [11] shows that
HAP as a cause of septic shock was associated with a poor
outcome and significantly higher mortality (82%; p < 0.03)
compared to wound infections and urinary tract infections.
ARDS = acute respiratory distress syndrome; AUC = area under curve; CRP = C-reactive protein; HAP = hospital-acquired pneumonia; ICU = inten-
sive care unit; IL = interleukin; TNF = tumor necrosis factor.
Critical Care Vol 9 No 6 von Dossow et al.
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Several studies indicate that a causal relationship exists
between the surgical injury and the predisposition of these
patients to develop infectious and septic complications
[12,13]. The excessive inflammatory response with alteration
of cell-mediated immunity following major surgery appears to
be responsible for the increased susceptibility to subsequent
infection and sepsis [13]. In particular, the regulation of the
inflammatory response in bacterial pneumonia is dependent
on complex interactions between alveolar macrophages, poly-
morphonuclear leukocytes, immune cells and local production
of both pro- and anti-inflammatory cytokines as well as vascu-
lar adhesion molecules [14-16]. The cytokines secreted by
phagocytes in response to infection include tumor necrosis
factor (TNF)-α, IL-1β, IL-6, IL-8 as well as IL-10 [14]. Inter-
leukins are increasingly recognized as early mediators of the
host inflammatory response to a variety of infectious agents.
On one hand, cytokines can leak from the inflammatory sites in
the lung as the normal compartmentalization of inflammation is
lost during severe local infection [17,18]. Alternatively,
cytokines may be produced in the systemic compartment in
response to bacterial products, such as endotoxin, that leak
from the lungs into the circulation [19-21]. Parsons et al. [22]
have provided the strongest evidence to date that IL-6, IL-8
and IL-10 are useful circulating markers for the intensitiy of the
inflammatory response in the lungs and the prognosis of
patients at the onset of lung injury. High elevated plasma levels
of IL-6 and IL-8 have been associated with higher mortality
rates [23-25].
To the best of our knowledge, no other study to date has inves-
tigated the systemic progression of HAP to septic shock with
respect to the pattern of circulating cytokines in surgical
patients.
The primary aim of this study was to investigate whether
patients, within four hours of a HAP diagnosis, differed in their
pro- and anti-inflammatory cytokine and adhesion molecule
patterns before the development of septic shock. The second-
ary aim was to evaluate whether any of these markers had a
predictive value for the progression of HAP to septic shock.
Materials and methods
This study was approved for an operative ICU. After receiving
both the approval of the institutional ethics commitee and writ-
ten informed consent from patients relatives or legal repre-
sentatives, 76 patients were included. All patients were
surgical patients (major abdominal, neurosurgical, trauma).
The patients were allocated to two groups: HAP without sep-
tic shock and HAP with subsequent septic shock. HAP was
diagnosed according to the criteria of the American Thoracic
Society 1996 [2]. Patients were included within 4 h after the
onset of HAP. Exclusion criteria were patients younger than 18
years old, acute myocardial ischemia, any corticosteroid ther-
apy or chemotherapy, acute respiratory distress syndrome
(ARDS), acute lung injury and heart insufficiency. A diagnosis
of pneumonia was made if systemic signs of infection were
present, new or worsening infiltrates were seen on the chest
X-ray, and new onset of purulent sputum or a change of spu-
tum with bacteriologic evidence in the endotracheal aspirate
was found [26,27]. Subsequent septic shock criteria were
defined as outlined in the Consensus Conference 1992 [28].
In particular, we defined early (within 12 h of onset) and late
(within 72 to 96 h of onset) stages of septic shock.
The collection of blood samples for the analysis of immune
mediators, were drawn in all patients (with and without subse-
quent septic shock) at the time of HAP diagnosis within the
first 4 h after onset. In patients with HAP and subsequent sep-
tic shock, blood samples were obtained at the early stage
(within 12 h of onset) as well the late stage (within 72 to 96 h
of onset) of subsequent septic shock.
All blood samples were collected in sterile tubes and cen-
trifuged; the supernatants were stored in liquid nitrogen at
-70°C. All mediators were analyzed at 23°C using a sandwich
enzyme-linked immunosorbent assay (Quantikine™ Immu-
noassay Kit, R&D Systems, Minneapolis, MN, USA). Detection
limits were: IL-1β, 0.1 pg/ml (intra- and interassay variation
coefficients 3.0% and 12.5%, respectively); IL-6, 3 pg/ml
(4.6%, 12.1%); IL-8, 8 pg/ml (5%, 11.1%); IL-10, 5 pg/ml
(3.0%, 7.0%); TNF-α, 4.4 pg/ml (4.6%, 5.8%); E-selectin, 2
ng/ml (3.2%, 6.4%).
Table 1
Basic patient characteristics and etiology of pneumonia at the time of admission to the intensive care unit
Characteristics and etiology (n =
76)
Pneumonia without subsequent
septic shock (n = 47)aPneumonia with subsequent
septic shock (n = 29)ap value
Age (years) 49 (36–58) 54 (47–69) 0.18
BSA (m2) 1.9 (1.8–2.0) 1.9 (1.8–2.0) 0.64
APACHE III 39 (31–50) 38 (32–53) 0.58
MOF score 3.0 (1.0–4.0) 4.5 (2.7–6.0) 0.09
Infections Gram+/Gram- 18/21 8/15 = 0.99
aData are expressed as median (25/75 percentile). APACHE III, Acute Physiology and Chronic Health Evaluation III score at the time of admission
to the intensive care unit; BSA, body surface area; Gram+, Gram-positive; Gram-, Gram-negative; MOF, Multiple Organ Failure score.
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Routine laboratory parameters, including leucocytes, C-reac-
tive protein (CRP), lactate and platelets, were determined two
times a day. All patients were mechanically ventilated and
received a continuous analgosedation with either propofol/
fentanyl or midazolam/fentanyl. Basic patient characteristics,
the microbiological etiology pneumonia, the Acute Physiology
and Chronic Health Evaluation (APACHE) III score [29] and
the Multiple Organ Failure (MOF) score [30] were docu-
mented. The researchers who performed the laboratory analy-
ses were blinded to data collection, diagnosis of pneumonia
and ICU outcome. Furthermore, the diagnosis of HAP made by
clinicians on the ICU was seen and confirmed by two blinded
researchers.
A radial artery catheter and a central-venous catheter were
inserted as routine monitoring in all patients. A pulmonary
artery catheter was inserted as routine cardiovascular monitor-
ing for the 29 patients with subsequent septic shock. Arterial
and mixed-venous blood gases were performed in all patients
with septic shock to determine oxygen-transport related varia-
bles, in particular oxygen delivery and oxygen consumption via
standard formulae. Volume resuscitation (crystalloids, colloids
and blood transfusions) was performed to achieve an optimal
left arterial pressure, which was estimated by the pulmonary
capillary wedge pressure reaching the plateau value for left
ventricular stroke work. If the cardiac index was <2.5 l/minute/
m2, 3 to 10 ug/kg/minute dobutamine was administered to
maintain the cardiac index between 3.0 and 3.5 l/minute/m2. If
mean arterial pressure was below the level of 70 mmHg, nore-
pinephrine was administered to obtain a mean arterial pres-
sure between 70 and 90 mmHg [31]. Steroids were given in
patients at the time of septic shock according to additive ther-
apy, especially in patients who exhibited a poor response to
the primary vasopressor agent [31].
Statistics
All data are expressed as median and 25/75 percentile. Sta-
tistical analysis between groups (HAP patients with and with-
out subsequent septic shock) was performed using the Mann-
Withney U test (intergroup analysis). The receiver operating
curve was plotted to provide a graphical presentation of the
relationship between sensitivity and specificity of the media-
tors covering all possible diagnostic cutoff levels. The area
below the receiver operating curve (AUC) represents the
probability of septic shock developing in a patient with pneu-
monia [32]. Statistical analysis of the pneumonia patients with
subsequent septic shock (intragroup analysis) was performed
using the Friedman test to show significant differences
between pneumonia and early and late septic shock. When
the global test revealed a significant difference, the Wilcoxon
matched-pairs signed-rank test was then used to decide
whether or not pneumonia and early and late septic shock dif-
fered locally. The Chi-square test was used to test statistical
differences between dichotomous variables. A p < 0.05 was
considered significant.
Results
Out of a total of 76 patients with HAP, 29 patients developed
subsequent septic shock. Basic patient characteristics as well
as the etiology of pneumonia (Gram-positive/Gram-negative)
did not differ significantly between the two groups (Table 1).
In the pneumonia group without septic shock, Gram-positive
species were isolated from 18 patients (Staphylococcus
aureus, Enterococcus faecium, Enterococcus faecalis),
whereas Gram-negative species were isolated from 21
patients (Pseudomonas aeruginosa, Proteus mirabilis, Kleb-
siella pneumoniae, Enterobacter cloacae). In the pneumonia
group with subsequent shock, eight patients had Gram-posi-
tive pulmonary infection (Staphylococcus aureus, Enterococ-
cus faecium, Enterococcus faecalis), whereas Gram-negative
species were isolated from 15 patients (Pseudomonas aeru-
ginosa, Proteus mirabilis, Klebsiella pneumoniae, Entero-
bacter cloacae).
At the 'diagnosis of pneumonia', the clinical and laboratory
findings did not significantly differ between the groups (Table
2). The time from admission to the ICU to the time of diagnosis
of pneumonia did not differ between the groups (p < 0.37;
Table 2
Scoring systems and laboratory findings at the time of hospital-acquired pneumonia diagnosis
Clinical and laboratory findings (n = 76) Pneumonia without subsequent
septic shock (n = 47)aPneumonia with subsequent
septic shock (n = 29)ap value
Time from admission to onset of pneumonia (h) 33.0 (4.0–87.0) 42.0 (22.0–78.0) 0.37
CRP (U/l) 60.0 (33–101) 80.0 (71.0–135.0) 0.13
Leukocytes (G/l) 12.7 (10.1–15.0) 12.6 (4.4–13.3) 0.18
Platelets (G/l) 175.0 (135.0–325.0) 193.0 (79.0–435.0) 0.51
Lactate (mmol/l) 1.3 (1.1–1.7) 1.5 (1.2–2.4) 0.05
PaO2 ratio/FIO2350 (300–375) 350 (310–385) 0.24
aData are expressed as median (25/75 percentile). CRP, C-reactive protein; FIO2, inspired oxygen concentration; G/l, cells × 109 per liter; PaO2,
arterial oxygen pressure.
Critical Care Vol 9 No 6 von Dossow et al.
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Table 2). In the pneumonia group with subsequent septic
shock, the time from diagnosis of pneumonia to the onset of
early septic shock was 75 h (range 30 to 85 h), from early sep-
tic shock to late septic shock 78 h (range 17 to 103 h). None
of the patients of the septic shock group had septic shock at
the time of diagnosis of pneumonia. The progression from
pneumonia to septic shock showed a significant increase in
APACHE III and MOF scores as well in levels of leucocytes,
although there was no significant increase in the levels of C-
reactive protein, lactate and platelets (Table 3).
Immune modulating mediators and clinical parameters
at the onset of pneumonia and during subsequent septic
shock
At the 'diagnosis of pneumonia', TNF-α, IL-1β, IL-6, IL-8, IL-10
and E-selectin were significantly increased in those patients
who had subsequent septic shock, compared to patients with
pneumonia without subsequent septic shock (Table 4). The
AUC of IL-1β, IL-6, IL-8 and IL-10 ranged from 0.80 to 0.82
(Fig. 1a,b). In addition, routine laboratory parameters, such as
levels of lactate, leucocytes and C-reactive protein as well as
APACHE III and MOF scores, did not differ between the
groups. The AUC of leukocytes and C-reactive protein ranged
from 0.34 to 0.58 (Fig. 1c).
TNF-α and E-selectin increased significantly in 'early' septic
shock. From 'early' to 'late' septic shock, significant decreases
were observed in TNF-α, IL-1β, IL-6, and E-selectin (Table 3).
Hemodynamic and oxygen-related parameters in septic
shock patients
None of the patients in both the non-septic and the septic
shock group had pre-existing ARDS or fulfilled the criteria of
ARDS at the diagnosis of pneumonia. None of the patients of
either group had bilateral infiltrates in the chest X-ray as a radi-
omorphological correlate for the diagnosis of ARDS. The heart
rate of patients with septic shock was significantly higher in
the late phase of septic shock. In addition, oxygen consump-
tion was significantly higher in early septic shock.
ICU stay and outcome in patients without and with septic
shock
ICU stay did not differ between both groups. In contrast, the
survival rate was significantly higher in patients without septic
shock (Table 5). For 12 patients (5 patients without subse-
quent septic shock and 7 patients with subsequent septic
shock), initial inappropriate antibiotic therapy was changed
immediately according to the specific bacterial strains iso-
lated. No significant differences in inflammatory parameters
were found in these patients compared to patients who
received initial adequate therapy.
Discussion
The most important result of this study was the detection of an
already increased immune response with respect to circulat-
ing cytokines at the onset of HAP in all patients with subse-
quent septic shock compared to those without subsequent
septic shock. In particular, IL-1β, IL-6, IL-8 and IL-10 were
most predictive for the progression of septic shock (area
under the curve ≥ 0.80). Furthermore, in our study, laboratory
markers were not predictive for the progression of HAP to
septic shock, which is in accordance with other clinical studies
[11].
To the best of our knowledge, no other study to date has inves-
tigated the systemic progression of HAP to septic shock in
Table 3
Scores, laboratory findings and immune modulating parameters in hospital-acquired pneumonia patients with subsequent septic
shock
Clinical and laboratory
findings (n = 29)
Pneumonia with subsequent
septic shock (I)aEarly septic shock (II)aLate septic shock (III)ap valueb
MOF 4 (3–6) 6 (5–8) 7 (4–9) ≤ 0.01 (I-II, I-III)
APACHE III 38 (32–52) 56 (39–75) 66 (45–88) ≤ 0.01 (I-II, I-III)
CRP (U/l) 80 (71–135) 131 (76–260) 103 (44–225) 0.60
Leucocytes (G/l) 12.6 (4.4–13.3) 18.9 (14.9–26.5) 19.8. (14.0–29.4) ≤ 0.01 (I-II, I-III)
TNF-α (pg/ml) 12.0 (8.0–15.2) 21.0 (9.8–55) 12.0 (9.7–16.7) ≤ 0.01 (I-II, II-III)
IL-1β (pg/ml) 1.9 (1.4–2.0) 2.0 (1.7–2.85) 1.5 (1.2–1.9) ≤ 0.01 (II-III)
IL-6 (pg/ml) 367 (166–678) 773 (229–1,370) 253 (98–1,370) 0.01 (II-III)
IL-8 (pg/ml) 187 (106–410) 271 (108–638) 215 (98–1,370) 0.17
IL-10 (pg/ml) 47 (21–144) 45 (31–120) 26 (48–92) 0.16
E-selectin (ng/ml) 71 (42–115) 134 (78–184) 74 (48–92) ≤ 0.01 (I-II, II-III)
aData are expressed as median (25/75 percentile). bI-II, II-III and I-III: significant difference between measurement I and II, I and III, and II and III
(Wilcoxon matched-pairs signed-rank test) if globally found by Friedman test. APACHE III, Acute and Chronic Health Evaluation III score; CRP, C-
reactive protein; MOF, Multiple Organ Failure score; TNF, tumor necrosis factor.
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surgical patients with respect to immune modulating
cytokines, adhesion molecules, their systemic release and
their possible predictive value.
In our study, increased serum levels of IL-1β, IL-6, IL-8 and IL-
10 were found at the onset of HAP and had a predictive value
(area under the curve ≥ 0.80) for the progression to septic
shock. An increase in levels of IL-6 and IL-10 has been
reported after different types of surgery [33,34]. Furthermore,
different early proinflammatory cytokine responses, as well as
exaggerated increases in IL-10, are associated with later onset
of infections [35,34]. Brede et al. [35] demonstrated an imme-
diate increase in plasma TNF-α levels in peritonitis patients,
which was predictive for the development of subsequent sep-
tic shock. None of the patients had septic shock at the diag-
nosis of peritonitis, which is in accordance with our findings. In
addition, Sander et al. [36] found decreased IL-6/IL-10 levels
in patients immediately after surgery of the upper gastrointes-
tinal tract, which was associated with an increased risk of
postoperative infections. Spies et al. [37] reported an immedi-
ate increased IL-10 response, which was associated with the
later onset of postoperative infections. Even if the above men-
tioned studies are not fully comparable to our study, the post-
operative and early immediate increase of cytokines,
especially IL-10, IL-1β, IL-8 and IL-6, might be explained as an
exaggerated and imbalanced pro- and anti-inflammatory
immune response after surgery.
In general, a clinical complication of HAP is the dissemination
of bacteria from the pulmonary airspace into the bloodstream,
resulting in bacteremia concurrent with the localized infection
[38,39]. In addition to direct bacterial phagocytosis, alveolar
macrophages secrete a variety of cytokines and chemokines
capable of activating blood neutrophils and monocytes in the
pulmonary microenvironment [38]. Furthermore, inability to
clear bacteria from the bloodstream can lead to a high expo-
sure to endotoxin and subsequent septic shock [39,40]. The
cytokines secreted by phagocytes in response to infection
include TNF-α, IL-1β, IL-6, IL-8 and IL-10 [14]. In accordance
with our findings, Bonten et al. [23] showed that ventilator-
associated pneumonia in patients with severe sepsis and sep-
tic shock was accompanied by increased levels of IL-6 and IL-
8 at the time of diagnosis, and even two days after diagnosis,
Table 4
Immunmodulatory parameters at the time of hospital-acquired pneumonia diagnosis
Immunmodulatory parameters (n = 76) Pneumonia without subsequent
septic shock (n = 47)aPneumonia with subsequent
septic shock (n = 29)ap value
TNF-α (pg/ml) 7.0 (6.0–9.0) 12.0 (8.0–15.0) ≤ 0.01
IL-1β (pg/ml) 1.2 (1.0–1.4) 1.85 (1.3–2.0) ≤ 0.01
IL-6 (pg/ml) 64.0 (29.0–155.0) 367.0 (166.5–678.1) ≤ 0.01
IL-8 (pg/ml) 73.0 (52.0–103.0) 187.0 (106.1–410.0) ≤ 0.01
IL-10 (pg/ml) 15.0 (8.0–24.0) 47.0 (21.7–144.0) ≤ 0.01
E-selectin (ng/ml) 34.0 (24.0–56.0) 71.0 (42.5–115.0) ≤ 0.01
aData are expressed as median (25/75 percentile). p < 0.05. E-selectin, endothelial leukocyte adhesion molecule; TNF, tumor necrosis factor
alpha.
Figure 1
Predictive value of immune modulating parameters and conventional laboratory parameters at hospital-acquired pneumonia diagnosisPredictive value of immune modulating parameters and conventional
laboratory parameters at hospital-acquired pneumonia diagnosis. (a)
Area under the receiver operating curve (AUC) for IL-6, IL-8 and IL-1β
(*p < 0.05). (b) AUC for IL-10 (*p < 0.05). (c) AUC for C-reactive pro-
tein (CRP). Ns, not significant.